Field
The present invention relates to a pool cleaner, and, more specifically to a pool cleaner with automatic cleaner traction correction to account for different swimming pool surfaces and conditions.
Related Art
Swimming pools commonly require cleaning. Beyond the treatments and filtration of pool water, the bottom wall and side walls of a pool are scrubbed regularly. Automated pool cleaning devices, e.g., swimming pool cleaners, have been developed to routinely navigate about the pool walls, cleaning as they go.
During cleaning, the pool cleaner will traverse the pool surfaces brushing or scrubbing the debris therefrom. The pool cleaner can be designed to operate at a certain speed while traversing certain walls or operating in certain modes. However, due to many different variables such as obstacles in the pool, changes in pressure, and different pool surfaces, the speeds and angular rates of the pool cleaner can change to an undesirable speed while cleaning the pool.
In order to overcome this problem, pool cleaners can be designed to have a setpoint, which is a desired target for a process variable. In the case of maintaining the angular rate of a pool cleaner, the process variable could be the angular rate of the pool cleaner. Accordingly, the pool cleaner can monitor the angular velocity of the cleaner and if there is an error, the pool cleaner can adjust the motors speed instruction in an effort to achieve the setpoint on the angular velocity of the cleaner.
A pool cleaner can adjust the motor speed instruction based on a “Proportional Integral Derivative” or “PID” control loop formula which takes into account the present error, historical error and future error in deviations from the desired set-point on the angular velocity (or other process variable). In other words, a PID control loop accounts for the input at the present moment, things learned from historical data, and the future projected data. Each one of the three parts to the PID control loop can have a constant factor or coefficient associated with it, also known respectively as “proportional gain,” “integral gain,” and “derivative gain.” Each “gain” represents how much emphasis or weight to put on that part of the formula. In some situations, it could be desirable to focus only on present and historical errors, in which case the gain for the D component is zero, which would result in a “PI” control loop. Alternatively, it could be desirable to focus only on the present error, in which case the gain for the I and D components are zero, which results in a “P” control loop. As used herein, the term “PID” control module can be understood to include within its scope, a “PI” control module (in which the derivative gain is 0) and a “P” control module (in which the integral gain and the derivative gain is 0).
The process of pre-assigning gain values can be called “tuning.” The issue with tuning pool cleaners is that some fixed set of gain values may perform well on some pool surfaces while not performing well on other surfaces because of the difference in traction on the wheels of the pool cleaner. Moreover, pool surfaces can vary greatly from one pool to another. The surfaces can range from concrete, vinyl, fiberglass, tile, and many variations in between. Accordingly, it is difficult to tune the gain values in advance because it cannot be known what pool surface the cleaner will clean.
Therefore, there exists a need for a pool cleaner designed with the ability to automatically account for the differences in traction on any pool surface it may encounter while cleaning.